This invention refers to construction of tunnels of large diameter under water, for example those used for road and rail traffic.
Common existing methods of constructing tunnels under water are by boring and lining, and also by pre-fabricating them in long sections which are floated to site and sunk in a trench, the sections being generally of a length ten or more times the tunnel diameter and being constructed in a drydock or on a slipway.
Objects of the invention are to provide a simpler and faster method of construction of pre-fabricated tunnels without the use of divers and to reduce the size of open trench and the time it is open.